Field of the Disclosure
Embodiments of the present invention relate to a liquid crystal display (LCD) device, and more particularly, to a polarizing plate formed on a lower substrate or an upper substrate of an LCD device.
Discussion of the Related Art
A liquid crystal display (LCD) device is advantageous in that it enables low power consumption and portability. Due to these advantages, the LCD device is widely used in various fields, for example, notebook computer, monitor, spacecraft, aircraft, and etc.
The LCD device may include a lower substrate, an upper substrate, and a liquid crystal layer between the lower and upper substrates. As an electric field is applied to the LCD device, liquid crystal molecules of the liquid crystal layer are aligned so that a light transmittance is controlled, and thus an image is displayed on the LCD device.
Hereinafter, a related art LCD device will be described with reference to the accompanying drawings.
FIG. 1 is a cross sectional view illustrating the related art LCD device.
As shown in FIG. 1, the related art LCD device may include an upper substrate 10, a lower substrate 20, a liquid crystal layer 30, an antistatic layer (static-electricity prevention layer) 40, an upper polarizing plate 50, and a lower polarizing plate 60.
Although not shown, a light shielding layer for prevention of light leakage is provided on one surface of the upper substrate 10, and more particularly, a lower surface of the upper substrate 10 facing the lower substrate 20. Also, a color filter layer for a color realization is provided in a region between each light shielding layer.
Although not shown, a thin film transistor functioning as a switching device is formed on one surface of the lower substrate 20, and more particularly, an upper surface of the lower substrate 20 facing the upper substrate 10. Also, a pixel electrode is formed and connected with the thin film transistor, and a common electrode is arranged in parallel to the pixel electrode, wherein both the pixel and common electrodes are provided to form an electric field.
The liquid crystal layer 30 is formed between the upper substrate 10 and the lower substrate 20, and an alignment direction of the liquid crystal layer 30 is controlled by the electric field formed through the use of pixel and common electrodes.
The antistatic layer (static-electricity prevention layer) 40 is formed on an upper surface of the upper substrate 10. The antistatic layer 40 is provided to prevent static electricity from being generated for a manufacturing process. In more detail, as described above, the light shielding layer and the color filter layer are formed on the lower surface of the upper substrate 10. For a process of forming these layers such as the light shielding layer and the color filter layer, the static electricity may be generated on the upper substrate 10 due to a contact with a plurality of processing and transferring apparatuses. In order to remove the static electricity, the antistatic layer 40 is formed of a conductive material, for example, Indium Tin Oxide (ITO), on the upper surface of the upper substrate 10.
The upper polarizing plate 50 is formed on an upper surface of the antistatic layer 40. The upper polarizing plate 50 may include an upper polarizer 51 having a predetermined optical axis, a first upper protection film 53 formed on one surface of the upper polarizer 51, a second upper protection film 55 formed on the other surface of the upper polarizer 51, and an upper adhesive 57 formed on a lower surface of the second upper protection film 55 so as to adhere the antistatic layer 40 and the upper polarizing plate 50 to each other. The upper polarizer 51 is manufactured by dyeing PVA (polyvinyl alcohol) with iodine. Since PVA is very weak in moisture, the first and second upper protection films 53 and 55 are respectively attached to both surfaces of the upper polarizer 51.
The lower polarizing plate 60 is formed on a lower surface of the lower substrate 20. The lower polarizing plate 60 may include a lower polarizer 61 having a predetermined optical axis, a first lower protection film 63 formed on one surface of the lower polarizer 61, a second lower protection film 65 formed on the other surface of the lower polarizer 61, and a lower adhesive 67 formed on an upper surface of the second lower protection film 65 so as to adhere the lower substrate 20 and the lower polarizing plate 60 to each other. In the same manner as the upper polarizer 51, the lower polarizer 61 is also manufactured by dyeing PVA (polyvinyl alcohol) with iodine. In order to overcome the PVA weakness related with moisture, the first and second lower protection films 63 and 65 are respectively attached to both surfaces of the lower polarizer 61.
However, the related art LCD device may have the following disadvantages.
A transmission wavelength for each of the upper polarizer 51 and the lower polarizer 61 may be optimized by complementary-color processes after dyeing PVA with iodine and stretching. However, it is very difficult to control the process of optimizing the transmission wavelength. Also, the upper polarizer 51 and the lower polarizer 61 may shrink due to a restoring force. In addition, a thinness of the LCD device has a limitation due the first and second upper protection films 53 and 55 and the first and second lower protection films 63 and 65.
Also, the antistatic layer 40, which is formed of ITO, may corrode due to the iodine included in the upper polarizer 51.